Changes

Loudness depends on frequency, intensity and distance. Scientists Weber and Fechner found that dividing the intensity of a note by the softest intensity it can be heard at and then finding the logarithm of the result approximates how loud the note will seem. When the tone seems 1 bel louder, the intensity is ten times stronger. Humans can tell the difference between tenths of a bell, so loudness is measured in decibels. Using a sound meter, how much street sound a closed window keeps out of a room can be calculated with algebra.<ref name="Harris & Hemmerling, Chapter 19" />

Loudness depends on frequency, intensity and distance. Scientists Weber and Fechner found that dividing the intensity of a note by the softest intensity it can be heard at and then finding the logarithm of the result approximates how loud the note will seem. When the tone seems 1 bel louder, the intensity is ten times stronger. Humans can tell the difference between tenths of a bell, so loudness is measured in decibels. Using a sound meter, how much street sound a closed window keeps out of a room can be calculated with algebra.<ref name="Harris & Hemmerling, Chapter 19" />

As a sound wave gets a bigger diameter by moving away from the sound source, its intensity gets less. Sound intensity getting less because of distance is called attenuation. An attenuated sound has become weaker because of distance traveled and an amplified sound has been made stronger. The increase in loudness is called the gain. There are algebraic problems about whether a speaker is loud enough for a listener at a given distance and so forth. Each problem would take a long section to explain well.<ref name="Harris & Hemmerling, Chapter 19" />

As a sound wave gets a bigger diameter by moving away from the sound source, its intensity gets less. Sound intensity getting less because of distance is called [[attenuation]]. An attenuated sound has become weaker because of distance traveled and an amplified sound has been made stronger. The increase in loudness is called the gain. There are algebraic problems about whether a speaker is loud enough for a listener at a given distance and so forth. Each problem would take a long section to explain well.<ref name="Harris & Hemmerling, Chapter 19" />

 

===Sound quality===

===Sound quality===

Quality of a note refers to differences in the sound produced by different sources. A tone from a single frequency is a pure tone. However, a violin’s string vibrates in more than one way at the same time. The tone from the entire length moving back and forth is the fundamental tone. The tones from part of the length moving one way while another part is moving another way are called overtones, also called harmonics. They happen at the same time as the fundamental, and add to and subtract from the fundamental’s wave. The note played is the fundamental. Its quality is affected by the length’s harmonics. Two good singers have a different sound quality, partly because their different vocal chords produce different overtones.<ref name="Harris & Hemmerling, Chapter 19" />

Quality of a note refers to differences in the sound produced by different sources. A tone from a single frequency is a pure tone. However, a violin’s string vibrates in more than one way at the same time. The tone from the entire length moving back and forth is the fundamental tone. The tones from part of the length moving one way while another part is moving another way are called overtones, also called harmonics. They happen at the same time as the fundamental, and add to and subtract from the fundamental’s wave. The note played is the fundamental. Its quality is affected by the length’s harmonics. Two good singers have a different sound quality, partly because their different vocal chords produce different overtones.<ref name="Harris & Hemmerling, Chapter 19" />